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Differences in vascular permeability between normal tissue and a tumor. Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (lymphocytes on their way to the site of inflammation) in and out of the vessel.
Diffusion occurs through the walls of the vessels due to a concentration gradient, allowing the necessary exchange of ions, molecules, or blood cells. The permeability of a capillary wall is determined by the type of capillary and the surface of the endothelial cells. A continuous, tightly spaced endothelial cell lining only permits the ...
A capillary is a small blood vessel, ... Capillary permeability can be increased by the release of certain cytokines, anaphylatoxins, or other mediators ...
The rate at which fluid is filtered across vascular endothelium (transendothelial filtration) is determined by the sum of two outward forces, capillary pressure and colloid osmotic pressure beneath the endothelial glycocalyx (), and two absorptive forces, plasma protein osmotic pressure and interstitial pressure (). The Starling equation is the ...
Because large and negatively charged proteins have a low permeability, they cannot filtrate easily to Bowman's capsule. Therefore, the concentration of these proteins tends to increase as the glomerular capillaries filtrate plasma, increasing the oncotic pressure along the glomerular capillary. [6]
With the loss of pericytes, microaneurysms form in the capillaries. In response, the retina either increases its vascular permeability, leading to swelling of the eye through a macular edema, or forms new vessels that permeate into the vitreous membrane of the eye. The end result is reduction or loss of vision. [36]
Throughout the body, dissolved compounds have an osmotic pressure. Because large plasma proteins cannot easily cross through the capillary walls, their effect on the osmotic pressure of the capillary interiors will, to some extent, balance out the tendency for fluid to leak out of the capillaries. In other words, the oncotic pressure tends to ...
Capillary bed permeability, which varies between tissues. Blood-brain barrier: this is located between the blood plasma in the cerebral blood vessels and the brain's extracellular space. The presence of this barrier makes it hard for a drug to reach the brain.